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Database: Relational: Definition: What is the definition of a relational database?

Jul 6th, 2008 13:28
Knud van Eeden, dman,


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--- Knud van Eeden --- 15 March 2005 - 06:01 pm ----------------------
Database: Relational: Definition: What is the definition of a 
relational database?
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A relational database is a database organization method that links
files together as required.
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A relational database is a collection of 1 or more tables which are
linked together via common fields (e.g. a unique identification 
number).
By creating this links between tables, you create thus 'relations'.
Hence the name 'relational' database.
A relationship between a pair of tables is established implicitly
through matching values of a shared field.
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A relational database stores data in relations, which the user
perceives as tables.
Each relation is composed of tuples, or records, and attributes, or
fields.
The physical order of the records or fields in a table is completely
unimportant.
Each record in the table is identified by a field that contains a
unique value.
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The term 'relational database' was coined in 1970 by Edgar Codd, whose
objective was to easily accommodate a user's ad hoc request for
selected data.
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In non-relational database systems (e.g. hierarchical, network),
records in one file contain embedded pointers to the locations of
records in another, such as customers to orders and vendors to
purchases.  These are fixed links set up ahead of time to speed up
daily processing.
---
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Conceptually, a relational database can be pictured as a set of
spreadsheets in which rows from one spreadsheet can be related to rows
from another. In reality, the theory behind databases is much more
complex. Each 'spreadsheet' in a database is called a table. As with a
spreadsheet, a table is made up of rows and columns.
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Book: see also:
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[book: author = Greenspan, Jay / Bulger, Brad - title = MySql/PHP 
Database Applications - ISBN = 0-7645-3537-4 - p. 8 'What has happened 
here is that we have created a relationship between these two tables - 
hence the name "relational" database']
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[book: author = Reese, George - title = database programming with JDBC 
and Java - ISBN = 1-56592-270-0 - p. 13 'what is a relational 
database']
---
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Internet: see also:
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Database: Language: SQL: Overview: Can you give an overview of links 
about SQL?
http://www.faqts.com/knowledge_base/view.phtml/aid/32811/fid/54
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